Manufacture of very thin wires



May 10, 1927. 1,627,971

- G. L. HERTZ MANUFACTURE OF VERY THIN WIRES Y Filed April 22.1925

INV'ENTOR. I

Patented May 10, 1927;

.UNITED" STATES PATENT OFFICE.

GUSTAV LnDwIG nnn'rz, or Einnnovmr, NETHERLANDS, Ass xenon 'ro N. v. 'rmmrs' GLOEILAMPENFABBIEKEN, or EINDHOVEN, nnrnnnmns- MANUFACTURE OI. VERY THIN WIRES.

, Application filed April 22,1825, Serial No. 25,164, and in the Hetl eflandl June 18, 1924.

This invention relatesto a process for the manufacture of very *thin. wires, more particularly of wires having a diameter of the extremely suitable for the manufacture of order ofsome microns. In ractice thin .wires such asmetal wires can requently be made bymeans of a drawin process. Ac-

cording to such a processt e diameter of little rods or thicker wires can be reduced by means of drawing dies. These drawing dies may consist, for exam'le, of diamond through which a hole is bored corresponding to the diameter of the wire one wishes to manufacture. Vith the aid of drawing dies it is impossible, however, to draw. wires of a very small diameter, because such wires break'during the drawing process. The in vention has for its object-to provide a proc-, css according to which verythin wires can be easily produced without the use of drawing dies.

According to the invention the process for the manufacture ofvery thinwires consists in connecting wires of larger diameter as a cathode 1n a glow discharge at such a current. density that disintegraton .of the cathode occurs. It is known that in a glow dischargesclisintegrationof the cathode occurs if the cur rent density exceeds a certain value. In

this case the potential drop atthe cathode is greater than the normal cathode drop.

It has been found that by establishing for a considerable time a glow discharge of sufficiently high current density between the wire which-is to bemadethinner and which for this purpose is connected as cathode, and an auxiliary anodefthe diameter of -the cathode wire decreases and that in this manner wires can be made having a diameter of 1 micron or even less.

It is perhaps not. unnecessary to observe that itis impossible to manufacture-thin wires from wires lot-larger diameter by caus-' ving. the latter to volatilize at a higher tem- -perature; Volatilization .is an unstable procels's, -f or an incandescent wire has; the highest temperature in-the thinnest places so that. the volatilization is strongest there where the wire is thinnest. .It is; obvious that this circumstance leads to breakage of.

' the wire. Disintegration,'on theother hand,

' is a stable processgin which the phenomena occurring during volatilization' do. not present themselves and which permits the manufacture-otthin'wires having a diameter which is practicallyequal over the whole length.

The process-according to the invention is very thin single crystal wires. The known processes for t e manufacture-of single crys tal wires do not permit the manufacture of.

a figure representing the apparatus withv which the process can be realized.

In the. figure a tungsten wire 2 .havin a. length of 2 decimetres and a diameter 0 microns and from which one wants to manufacture a very; thin wire, issealed at 3 and 4 into a glass. bulb v1, having a diameter of 6-.centimetres.- Besides, a second'wire 5, for example of nickel, is'sealed into the .bulb at 6 and 7. The wire 2 the-ends of which are electrically connected to each other,is connected to the wire 5 via a potentiometer in which a source of current having-a tension tungsten, bismuth, cadmium, thallium lead,

of .500 volts is indicated by 8v and a regu- 'lable resistance by 9, via a resistance 10 of 10.000 ohms and a galvanometer llwhich permits to read 0.1 milliampcre. The bulb .1 is filled with argon of apr'essure of 0.2v

millimetres of mercury. By so adjusting the sliding contact on the resistance 9 that the galvanometer indicates a; current of 1 milliampere, the current density will be sufliciently great to cause the cathode to disintegrate.

During thef disintegrating process the thickness of the cathode wire can be tested by measuring the resistance of said wire.

If the disintegrating, proces's .is continued until the resistance of the wire 2 is increased to about the twentyfold amount of the resistance of the original wire, it appears that the cathode wire has a diameter of but some microns. It is however possible to continue theprocess still further and to obtain thus wires having an even considerably smaller diameter. Whenthe diameter of the cathode Wire has been sufliciently reduced, the wire may be removed from the bulb 1 by breaking the seals 2 and 3.

Wires manufactured in accordance with this process are very suitable for the use as resistance thermometers in string galvanometers according to Einthoven and other ap paratus in which it is desirable to utilize 10 very thin wires.

What I claim is: 1. A process for the manufacture of very thin wires, characterized in that Wires of larger diameter are connected as cathode.

In testimony whereof I affix my signa- 20 ture, at the city of Eindhoven this 4th day of ApriL A. D. 1925.

GUSTAV LUDWIG HERTZ. 

